What is a telescope? This question could seem trivial however behind this global word, we discover two main species of instruments to observe the remarkable objects of our starry sky. The reflector telescopes room composed of winter whereas the refractor telescopes are only made of lenses. They space a many differences in between both of these categories, in terms of performances, durability and especially optical quality.

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Reflector telescopes

Principle the a reflector

The newton telescopes space the most widespread reflectors in the market since of their simple building process and their low cost. The light coming from a star goes within the optical tube and also is first reflected ~ above the primary mirror, located at the extremity. This major mirror is the grasp piece the the reflector. It has to collect and make the irradiate beams converging in the direction of the eyepiece holder, the aspect where we put our eyes. Here, it is essential to find a means to do the irradiate beams going the end of the tube. Therefore, a secondary mirror is installed next to the prior aperture the the telescope, allowing beams to it is in deviated ~ above the next of the telescope, and also so, to observe an image.

The asset of a reflector is its main mirror’s very big size. The larger the winter is, the brighter the objects show up in the eyepiece. However, a huge mirror could quickly emphasize the optical aberrations that the telescope.

Optical top quality of reflectors

Theoretically, getting a perfect round period of a star requires having actually a newtonian reflector made with a hyperbolic primary mirror. In fact, together a winter is fairly expensive and telescopes manufacturers pick rather a parabolic winter instead, far much easier to build. However, a parabolic mirror is dealing with a defect: the coma aberration i m sorry deforms and also elongates the star around the fields of view.

More often, the low-cost manufacturers perform not usage nor a hyperbolic neither a parabolic mirror but a spherical mirror. With such a geometry, you will never control to focus perfectly the photo of a star v your reflector, since of spherical aberration ; a delicate situation considering that astronomy requires to observe and also photograph faint and also diffuse celestial objects.

Reflectors in practice

Reflector telescopes are mostly open telescopes, meaning that the mirrors room exposed come the air, humidity and also dust. This is why they need to it is in manipulated v precision and attention. Because that example, a mirror generally exposed come this harsh environment might be much less reflective in ~ years, or placed it in a various way, its capability to reflect light decreases. To this point, the cleaning of the winter is very recommended, paying too much attention to the fragile optical parts while dismounting the telescope.

A crucial element no to be forgotten through a newtonian-like telescope is the necessity to collimate it. This procedure enables you come perfectly adjust the alignment of the telescope and must it is in done before each observation or astrophotography session. This should be ideally lugged out every time you watch or start an astrophotography session.

Finally, reflector telescopes are an initial choice instruments when you want to collection the many light together possible. However the side results are that you will require to understand in details the optical system and also should no be shy once you will have to modify or clean the mirrors, as discussed above.

Pros & Cons



Large mirror = much better light collecting capacityNo chromatic aberrations (colored fringes around stars)Relatively short costOptical quality frequently disappointingCollimation and also mirrors clean processesOpen tube = high vulnerability come dust, humidity..etcBulky and heavy
Refractor Telescopes

The rule of keplerian telescope is very similar to a monocular. The irradiate goes through the prior lens, an essential element do the irradiate beams

converging to the eyepiece holder, wherein we install an eyepiece or a camera.Because of their compactness and ligthness, refractor telescopes do not collection as much light as reflector but have a much more stable optical quality and also do no need any kind of adjustement from the user/observer.

Optical high quality of the reflectors

They have the specificity come let us observing the starry sky with an exceptional sharpness and also contrast. These features are yes, really appreciated in expensive observation and astrophotography.Nonetheless, store attention top top what form of refractor girlfriend choose. The cheapest room made of a solitary lens which undergoes the irradiate dispersion. Consequently, a star will not be a solitary color allude anymore but surrounded by colored rings. This is what we contact chromatic aberrration.

Today, there are different manners to remove this optical defect such as adding a 2nd lens to achieve a doublet telescope.

Stellina : a refractor motivated by astrophotographers

Most the amateur astrophotographers prefer a telescope who durability, compactness and also simplicity to use are far better than the quantity of light collected. Thus they select refractor telescopes fairly than reflectors.

benidormclubdeportivo.org has actually responded to this demand and also built a refractor telescope from scratch, assisted by one of the most reknown metrology activities in France : AiryLab.

The optical architecture is a Lanthane ED Doublet, permitting to decrease drastically chromatic aberration. A special treatment on the lenses has actually been used in stimulate to pick only the wavelength the interest and also reject every ultraviolet and infrared lights.

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All these optimizations carried into this telescope space just consisted of in a small, transportable and entirely automatic refractor. Refractors are thus a reliable selection for stargazers who desire a dependable, pratical and easy-to-use huge instrument.

Pros & Cons



Impressive contrast and sharpnessLight and also transportableClosed tube = protection versus humidity and dustMaintenance and cleaning almost nonexistentSmall diameter = less light collectedChromatic aberrationsHigher price